1. Technical Field
The present disclosure generally relates to debarker systems, and more specifically to mechanical ring debarkers.
2. Description of the Related Art
Rotary log debarkers, commonly referred to as ring debarkers, are used to remove bark to process logs into lumber and other wood products. Rotary log debarkers often have an array of swing arms pivotally mounted to a rotatable ring. Each of the swing arms has a knife. As a log moves towards an opening of the ring, the advancing log contacts and pushes against the swing arms carried by the rotating ring. The log drives the swing arms outwardly until the knives engage the periphery of the log. The knives are urged against the log to scrape off bark.
Rotary log debarkers are typically either air-seal debarkers in which fluid pressure is maintained between the ring and an external fluid source during debarking or air-cell debarkers which are fluidically isolated from an external fluid source during debarking. Air-seal debarkers often have external fluid sources in the form of air compressors capable of delivering pressurized air to air actuators carried in a ring. The air actuators are connected to the swing arms processing the logs. The force exerted by the knives on logs can be changed on the fly by adjusting the air pressure in the actuators. For the air seal ring to operate properly, fluid communication has to be maintained between the external air compressor and the actuators. Components at the interface of the rotating and stationary parts of the ring are susceptible to failure where there is a lack of proper lubrication. Such a failure can be expensive and can result in significant machine down time. For example, significant amounts of frictional heat can be generated between seal components sliding along one another. This heat can lead to seal damage (e.g., degradation at the interface of seal components), unwanted leaking of air, and ultimately failure of seal components.
Air-cell debarkers often have rotatable rings with lightweight air bags for actuating swing arms. Air-cell rings have no air seal components so they can be rotated at relatively high rotational speeds. Each air bag is connected to a lever arm installed on a pivoting shaft carrying a swing arm. When a log enters the debarker, an end of the log strikes and moves the swing arms outwardly. The bags are compressed as the swing arms rotate. The compressed air bags exert a force to actuate the swing arms inwardly even though the air bags are not in fluid communication with an external fluid source. Air-cell rings often provide nonlinear debarking forces versus displacement, thereby providing a force gradient suitable for removing different amounts of bark from logs of different sizes, since bark thickness is often related to log diameters. Unfortunately, conventional air-cell rings are not adjustable so as to provide different force gradients. Thus, air-cell debarkers often properly debark logs having a particular diameter but improperly debark logs of other sizes because a single force gradient may not be suitable to process logs with significantly different diameters.